Usage
- Tetrahydrozoline is prescribed for the temporary relief of minor eye redness, burning, and irritation caused by dry eyes, smog, swimming, dust, or smoke. It can also provide temporary relief from conjunctival congestion.
- Pharmacological Classification: It is classified as a sympathomimetic amine and a vasoconstrictor/decongestant.
- Mechanism of Action: Tetrahydrozoline acts as an alpha-adrenergic agonist, constricting the conjunctival blood vessels, which reduces eye redness. It also has some weak alpha2 activity. Some formulations contain lubricants for additional relief from dryness and irritation.
Alternate Names
- It is sometimes referred to as tetryzoline.
- Brand Names: Visine, Visine-A, Visine LR, Visine AC, Murine Plus, Clear Eyes, Opti-Clear, All Clear and many others. Formulation may slightly differ with each product.
How It Works
- Pharmacodynamics: Tetrahydrozoline stimulates alpha-adrenergic receptors in the arterioles of the conjunctiva, causing vasoconstriction and reducing eye redness. It may also cause mydriasis (pupil dilation) to a small extent.
- Pharmacokinetics:
- Absorption: When applied topically to the eye, absorption is minimal. Systemic absorption can occur with excessive or incorrect use.
- Metabolism and Elimination: Limited information is available regarding the metabolism and elimination of ophthalmic tetrahydrozoline. Absorbed tetrahydrozoline is likely to be metabolized primarily in the liver and excreted renally.
- Mode of Action: Tetrahydrozoline binds to alpha-adrenergic receptors on the smooth muscle cells of the conjunctival blood vessels. This binding activates the receptors, leading to vasoconstriction. It may also bind to some alpha2 receptors.
- Receptor Binding: Alpha-adrenergic receptor agonist.
- Elimination Pathways: Primarily hepatic metabolism followed by renal excretion. However, precise pathways are not fully characterized for the ophthalmic route.
Dosage
Standard Dosage
Adults: 1-2 drops in the affected eye(s) every 6-12 hours as needed. Do not use for more than 72 hours continuously.
Children: For children aged 2 years and above, the same dosage can be used under the supervision of a healthcare professional. The 0.05% concentration is preferred.
Special Cases:
- Elderly Patients: No specific dosage adjustments are typically required. Close monitoring for systemic side effects is advised.
- Patients with Renal Impairment: Use with caution. Monitor for systemic effects due to potential increased absorption.
- Patients with Hepatic Dysfunction: Use with caution as metabolism may be impaired.
- Patients with Comorbid Conditions: Use with caution in patients with glaucoma (narrow angles or pre existing), cardiovascular disease, hypertension, diabetes, and hyperthyroidism, and benign prostatic hyperplasia.
Clinical Use Cases
Tetrahydrozoline is not typically indicated for use in clinical settings like intubation, surgical procedures, mechanical ventilation, or the ICU. Its primary use is for temporary relief of minor eye redness and irritation.
Dosage Adjustments
Dose adjustments may be necessary for patients with severe renal or hepatic impairment. Consult a specialist for individualized dosing recommendations.
Side Effects
Common Side Effects
- Mild burning or stinging upon instillation
- Blurred vision
- Mydriasis
- Reactive hyperemia upon discontinuation (rebound redness)
Rare but Serious Side Effects
- Severe eye pain
- Vision changes
- Worsening redness or irritation lasting more than 72 hours
- Headache, dizziness
- Tremor
- Elevated blood pressure or heart rate, palpitations
Long-Term Effects
Prolonged use beyond 72 hours can lead to rebound redness and dependence. Chronic use can potentially damage the eye’s surface.
Adverse Drug Reactions (ADR)
Allergic reactions (rash, itching, swelling, difficulty breathing), though rare, can occur and require urgent medical attention.
Contraindications
- Hypersensitivity to tetrahydrozoline or any component of the formulation
- Narrow-angle glaucoma or predisposition to angle closure
- Use with MAO inhibitors or within 14 days of discontinuing MAO inhibitors
Drug Interactions
- May interact with other sympathomimetic drugs, potentially leading to additive systemic effects.
- May interact with beta-blockers, causing a decrease in the decongestant effect and potentially increasing blood pressure.
- Although no direct interactions have been reported with CYP450 enzymes, caution should be exercised in combination with drugs metabolized through these pathways.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: Not formally assigned. Animal data are lacking. Use only if clearly needed and after careful assessment of risks and benefits. It is advisable to opt for safer alternatives if available.
- Breastfeeding: It is unknown if tetrahydrozoline is excreted in breast milk. Caution is advised. If use is necessary, consider temporarily interrupting breastfeeding or using an alternative medication.
Drug Profile Summary
- Mechanism of Action: Alpha-adrenergic agonist causing vasoconstriction in the conjunctiva.
- Side Effects: Burning/stinging, blurred vision, mydriasis, rebound redness, allergic reactions (rare).
- Contraindications: Hypersensitivity, narrow-angle glaucoma, concurrent use with MAOIs.
- Drug Interactions: Sympathomimetics, beta-blockers.
- Pregnancy & Breastfeeding: Use with caution if benefits outweigh risks.
- Dosage: 1-2 drops in affected eye(s) every 6-12 hours; not to exceed 72 hours.
- Monitoring Parameters: Eye redness, irritation, pupil size, blood pressure, heart rate.
Popular Combinations
Tetrahydrozoline is often combined with lubricants like polyethylene glycol or povidone in some eye drop formulations for additional relief from dryness.
Precautions
- General Precautions: Do not use for more than 72 hours. Remove contact lenses before use and wait 10-15 minutes before reinserting.
- Specific Populations: As described above.
- Lifestyle Considerations: Avoid operating machinery until vision clears after application.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Tetrahydrozoline?
A: Adults and children over 2 years: 1-2 drops in the affected eye(s) every 6-12 hours, not to exceed 72 hours.
A: No. Remove contact lenses before use and wait 10-15 minutes before reinserting. Some formulations contain benzalkonium chloride, which can be absorbed by soft contact lenses.
Q3: Can pregnant or breastfeeding women use Tetrahydrozoline?
A: Use with caution only if clearly needed and after consulting a doctor. Safer alternatives are preferred.
Q4: What are the serious side effects of Tetrahydrozoline?
A: Severe eye pain, vision changes, worsening redness/irritation, headache, tremor, changes in heart rate/blood pressure, allergic reaction.
Q5: Can I use Tetrahydrozoline if I have glaucoma?
A: No. Tetrahydrozoline is contraindicated in patients with narrow-angle glaucoma.
Q6: How long can I use Tetrahydrozoline continuously?
A: Do not exceed 72 hours of continuous use.
Q7: What should I do if my eye redness doesn’t improve after using Tetrahydrozoline?
A: Consult an ophthalmologist. Continued redness may indicate a more serious underlying condition.
Q8: Can Tetrahydrozoline interact with other medications?
A: Yes, potentially with other sympathomimetics and beta-blockers. Inform your doctor about all medications you are taking.
Q9: What is rebound redness?
A: Rebound redness is a worsening of eye redness that can occur after discontinuing tetrahydrozoline, especially after prolonged use. It is caused by dilation of the blood vessels after the constricting effect of the drug wears off.
Q10: Can children use Tetrahydrozoline?
A: Yes, Children aged 2 and above can use tetrahydrozoline under adult supervision, with the 0.05% concentration preferred. For younger children, consult a pediatrician before use.
